1. Field of the Invention
The present invention relates to a method for monitoring tire pressure, and particularly a method for monitoring tire pressure by automatically comparing intensities of signals sent from different identifiers received by an antenna.
2. Description of the Related Art
The present invention proceeds from a method having the features indicated in the preamble of claim 1. A method of this kind is known from WO 93/16891, in which a combination of pressure sensor, transmitter, and transmission antenna, with respective allocated receiving antennas and a central electronic analysis system on the body, is used. The problem that arises with tire pressure monitoring systems of this kind is unequivocal allocation of the transmitters to the respective wheel position. In WO 93/16891 this problem of position recognition is solved as follows: the transmitters generate a signal divided into four segments, consisting of preface, identification signal, measurement signal, and conclusion. The central electronic analysis system can recognize the position based on the identification signal. Doing so, however, requires first performing an initialization during which the respective identification signal, linked to the respective position, is stored by the central electronic analysis performing an initialization during which the respective identification signal, linked to the respective position, is stored by the central electronic analysis system. To perform this initialization, the system must be manually switched into a "pairing" mode, and each individual transmitter must then be activated once in sequence. The system is then switched back into measurement mode until the transmitter positions change, e.g. if a wheel is changed. In a first variant, each wheel is associated with an antenna and a receiving element of its own, that are connected to a central evaluation unit. The central electronic receiving system assigned to each individual wheel receives signals from all wheels, with each signal arriving from a wheel being allocated to that receiving unit in which it produces the highest signal intensity. This allocation can be effected, and is intended to be effected, only in stationary condition of the vehicle. In a second variant of the known method, one manually switches a central analysis into the paring mode--likewise with the vehicle in stationary condition--preselects a specific wheel position, provokes an artificial pressure drop in that wheel, and then determines the identifier of the transmitted tire pressure signal and associates it to the respective wheel. In the case of both variants a suitably trained person must perform this initialization and subsequent allocating step each time a wheel is changed. In some circumstances it is therefore impossible, or possible only at the cost of safety, to perform a wheel change at any repair shop or at home. Flawless operation of the system cannot be guaranteed due to potential operating errors.
In WO 93/08036, the problem is circumvented by recording the data for the pressure sensors and the transmission electronics connected to them not by means of a central electronic analysis system on the body, but by means of a remote-control element. Said remote-control element comprises an LCD display device which makes it possible to read the tire pressure. To determine the tire pressure, the desired information must be interrogated at each individual wheel by means of the remote-control element. Although this method offers the advantage of an unequivocal allocation of readings, it does not allow tire pressure to be checked while driving.